Systems, methods, and devices for unicast and/or multicast link establishment and maintenance. A wireless transmit receive unit (WTRU) may send a link establishment request broadcast message, wherein the link may be for multicast, unicast, or groupcast. The WTRU may receive a link establishment response broadcast message and a connectivity report. The WTRU may then send a link establishment confirmation broadcast message once a multicast or unicast link has been established, at which point the WTRU may send and receive a multicast message. The link establishment request message may be sent based on one or more triggers: receiving a QoS flow, needing a new sidelink radio bearer, determining that a new QoS flow or radio bearer requires network controlled admission control, and/or receive a unicast and/or multicast establishment request. The WTRU may transmit a unicast and/or multicast usability signal (UMUS). The WTRU may preempt the established multicast or unicast link.